In recent years, a UV-LED device that emits ultraviolet light has been adopted as a light source of a UV irradiation device in order to reduce power consumption and to make the device size compact.
In an LED device, an LED element is encapsulated so as to be protected from a physical impact caused by the use thereof. In general, encapsulating with a resin is performed as a form of encapsulating. As the resin, for example, an epoxy resin, a silicone resin or the like is used. In a UV-LED device encapsulated with a resin, the resin deteriorates due to ultraviolet light emitted from a UV-LED element, and cracks occur in some cases.
As an encapsulated LED device superior in ultraviolet light tolerance (hereinafter sometimes referred to as “light resistance”), one in which an LED element is encapsulated by melting and bonding inorganic glass to the LED element is known (for example, see Patent Document 1). However, since this LED device involves a process of melting and bonding inorganic glass, there are cases where the LED element is damaged by high temperature (for example, 400° C.) during the melting and bonding process.
Accordingly, as an LED device utilizing the excellent light resistance of inorganic glass and the optical properties of inorganic glass lens to the utmost and in which an LED element is encapsulated without involving a high-temperature process, an LED device provided with a resin filled in a case for accommodating an LED element, and an inorganic glass lens placed on the case so as to cover the resin is known (for example, see Patent Document 2).